The invention relates to drive circuits.
The invention relates more particularly to a drive circuit for use in controlling a lamp driven by solar cells. Such lamps are used for all forms of lighting applications especially exterior light around dwelling places. The lamps are arranged to be driven by re-chargeable batteries provided with solar panels so that they rely mainly or solely on receiving charging current generated by the solar cells during day light hours.
Commonly a fluorescent tube or lamp is used and driven via an electronic ballast. Battery energy is used to provide a high frequency high voltage power source which is applied between the terminals of the lamp. The ballast consists of a multi-phase transformer with a free-running oscillator.
FR-A2561483 and GB-A2053592 disclose lamps including a solar cell and oscillator drive and using a heating element to warm up the lamp. EP-A0429716 discloses a lamp drive circuit having an oscillator, a transformer and a switch to control power supply to one of the elements; the circuit is arranged to delay application of power to the lamp at start up to allow the filament of the lamp to warm up.
In European application 9,191,479.3 a drive circuit is described which continually monitors the operations condition of the fluorescent lamp and automatically adjusts the power supply to compensate for charges and to correct the operating condition. In doing so or in any event, it has been found preferable or necessary to protect the condition of the battery especially because if some types of battery discharge beyond a certain level, they never recover.
It is an object of the invention to provide a lamp drive circuit incorporating battery condition protection arrangements.